阅读说明：本技术 一种层状高熵双硼碳化物陶瓷粉体及其制备方法 (Layered high-entropy diboron carbide ceramic powder and preparation method thereof ) 是由 孙国勋 王伟礼 孙晓宁 于 2021-01-19 设计创作，主要内容包括：本发明涉及高熵陶瓷材料技术领域,具体涉及一种层状高熵双硼碳化物陶瓷粉体及其制备方法,所述层状高熵双硼碳化物陶瓷粉体中层状高熵双硼碳化物的化学式为REB-2C-2,其中RE为Y,Ce,Gd,Dy,Er中的至少三种不同元素,各元素的摩尔比为1；制备方法为将至少三种金属氧化物、硼源和碳源球磨混合,然后将混合均匀的粉体压实得到致密化的坯体,再将坯体高温烧结得到层状高熵双硼碳化物块体材料,最后经过破碎和研磨制得层状高熵双硼碳化物粉体。以金属氧化物为原料采用碳/硼热还原法可以合成单一相且组分均匀的高熵双硼碳化物陶瓷粉体,该方法制备工艺简单,易于控制反应过程,无杂质引入,产品制备成本低,适合批量生产。(The invention relates to the technical field of high-entropy ceramic materials, in particular to layered high-entropy diboron carbide ceramic powder and a preparation method thereof, wherein the chemical formula of layered high-entropy diboron carbide in the layered high-entropy diboron carbide ceramic powder is REB 2 C 2 Wherein RE is at least three different elements of Y, Ce, Gd, Dy and Er, and the molar ratio of each element is 1; the preparation method comprises the steps of ball-milling and mixing at least three metal oxides, a boron source and a carbon source, then compacting the uniformly mixed powder to obtain a densified blank, sintering the blank at a high temperature to obtain a layered high-entropy diboron carbide block material, and finally crushing and grinding to obtain the layered high-entropy diboron carbide powder. The high-entropy diboron carbide ceramic powder with single phase and uniform components can be synthesized by taking metal oxide as a raw material and adopting a carbon/boron thermal reduction methodThe method has the advantages of simple preparation process, easy control of reaction process, no impurity introduction, low product preparation cost and suitability for batch production.)

1. The layered high-entropy diboron carbide ceramic powder is characterized in that the chemical formula of the layered high-entropy diboron carbide is REB₂C₂Wherein RE is at least three different elements of Y, Ce, Gd, Dy and Er, and the molar ratio of each element is 1.

2. The layered high-entropy diboron carbide ceramic powder according to claim 1, wherein at least three metal oxides, a boron source and a carbon source are mixed by ball milling, then the uniformly mixed powder is compacted to obtain a densified blank, then the blank is sintered at a high temperature to obtain a layered high-entropy diboron carbide block material, and finally the layered high-entropy diboron carbide powder is obtained by crushing and grinding.

3. The preparation method of the layered high-entropy diboron carbide ceramic powder according to claim 1 or 2, wherein the preparation method comprises the following steps:

(1) weighing at least three metal oxides, a boron source and a carbon source in proportion;

(2) adding a solvent and a ball milling medium, ball milling and mixing raw materials, and performing vacuum drying and sieving to obtain uniformly mixed powder;

(3) hydraulically compacting the uniformly mixed powder, and performing cold isostatic pressing to obtain a densified blank;

(4) carrying out normal-pressure high-temperature sintering treatment on the blank in vacuum or protective atmosphere to obtain a layered high-entropy diboron carbide block material;

(5) and crushing and grinding the block material after high-temperature sintering to finally prepare the layered high-entropy diboron carbide powder.

4. The method according to claim 3, wherein the metal oxide is at least three selected from the group consisting of yttrium oxide, cerium oxide, gadolinium oxide, dysprosium oxide, and erbium oxide.

5. The method of claim 3, wherein the boron source is boron carbide or boron nitride.

6. The method according to claim 3, wherein the carbon source is graphite powder or carbon black.

7. The production method according to claim 3, wherein in the step (1), the metal oxide powders are weighed in such an amount that the metal elements are in an equimolar ratio;

alternatively, in step (1), according to reaction equation A_xO_y+2xBN+(2x+y)C＝xAB₂C₂+xN₂+ yCO calculating the amount of BN and carbon source required by each metal oxide powder when the carbon/boron thermal reduction reaction occurs, and then adding to obtain the total amount of BN and carbon source;

alternatively, in step (1), according to reaction equation A_xO_y+x/2B₄C+(3/2x+y)C＝xAB₂C₂+ yCO calculation of the B required for each metal oxide powder to undergo the carbon/boron thermal reduction reaction₄C and the amount of the carbon source, and then adding to obtain B₄C and the total amount of carbon source.

8. The preparation method according to claim 3, wherein in the step (2), the ball milling rotation speed is 200-400 rpm, the ball milling time is 10-24 h, and the ball milling medium is selected from ethanol, propanol, methanol, acetone or water;

or, in the step (2), the vacuum drying temperature is 60-120 ℃, and the drying time is 10-24 hours.

9. The method according to claim 3, wherein in the step (3), the hydraulic compaction pressure is 8 to 15MPa, and the dwell time is 5 to 10 min;

or in the step (3), the cold isostatic pressing pressure maintaining pressure is 200-300 MPa, and the pressure maintaining time is 10-20 min.

10. The method according to claim 3, wherein in the step (4), the selected protective atmosphere is argon or helium;

or, in the step (4), the sintering process is as follows: heating to 1900-2300 deg.C at a rate of 5-20 deg.C/min, maintaining for 2-5 hr, and cooling to room temperature to obtain the final product.

Technical Field

The invention relates to the technical field of high-entropy ceramic materials, in particular to layered high-entropy diboron carbide ceramic powder and a preparation method thereof.

Background

Double boron carbide REB₂C₂(RE ═ Sc, Y, lanthanides and actinides) ceramics have a typical lamellar structure. The current research on double boron carbide ceramics mainly focuses on YB₂C₂And (3) research of ceramics. YB (Yb)₂C₂The ceramic has the excellent characteristics of high melting point, high strength, good chemical stability and the like, and has wide application prospect in the fields of ultrahigh temperature and the like.

The high-entropy ceramic is a multi-component single-phase solid solution ceramic material with nearly equimolar components. The high-entropy ceramic shows unique high-entropy effect and excellent mechanical, electrical and thermal properties, so that the high-entropy ceramic has wide demand prospect. At present, oxide, carbide, boride and nitride high-entropy ceramics have been successfully synthesized, and the above materials show excellent performance in some aspects. However, there has been no report on the preparation of layered high entropy diboron carbide ceramics.

Currently, YB is prepared₂C₂The ceramic method is mainly a solid-phase reaction method. Mixing Y powder, B powder and C powder by ball milling, arc melting and subsequent heat treatment to obtain YB₂C₂Ceramic powder. G.ZHao et al in YH₄、B₄C and graphite are used as raw materials, and YB is prepared through hot-pressing reaction₂C₂A ceramic. Because the price of the metal simple substance powder is relatively high, the metal simple substance powder is not suitable for YB₂C₂And preparing the double boron carbide ceramics in large scale.

Disclosure of Invention

In order to solve the defects in the prior art, the invention provides a layered high-entropy diboron carbide (REB)₂C₂) The ceramic powder and the preparation method thereof apply the carbon/boron thermal reduction method to the preparation of the layered high-entropy diboron carbide ceramic powder, and the prior art does not disclose such precedent.

Specifically, the technical scheme of the invention is as follows:

in the first aspect of the invention, the layered high-entropy diboron carbide ceramic powder is provided, and the chemical formula of the layered high-entropy diboron carbide is REB₂C₂Wherein RE is at least three different elements of Y, Ce, Gd, Dy and Er,the molar ratio of each element was 1.

In a second aspect of the present invention, a method for preparing the layered high-entropy diboron carbide ceramic powder according to the first aspect is provided as follows:

ball-milling and mixing at least three metal oxides, a boron source and a carbon source, compacting the uniformly mixed powder to obtain a densified blank, sintering the blank at a high temperature to obtain a layered high-entropy diboron carbide block material, and finally crushing and grinding to obtain the layered high-entropy diboron carbide powder.

The specific embodiment of the invention has the following beneficial effects:

(1) in the specific embodiment of the invention, the design concept of the high-entropy ceramic is introduced into the layered diboron carbide, so that the layered high-entropy diboron carbide ceramic powder is successfully synthesized, and the existing layered ceramic system is enriched;

(2) in the specific embodiment of the invention, the layered high-entropy diboron carbide ceramic powder is prepared by adopting a carbon/boron thermal reduction method, and solid solution powder with single phase and uniform components can be directly synthesized;

(3) the preparation method has the advantages of simple preparation process, easy control of reaction process, no impurity introduction, low product preparation cost and suitability for batch production.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, are included to provide a further understanding of the invention, and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments of the invention and together with the description serve to explain the invention and not to limit the invention.

FIG. 1 is a scanning electron microscope morphology of the layered high-entropy diboron carbide ceramic powder prepared in example 1 of the present invention;

FIG. 2 is an EDS spectrum of the layered high-entropy diboron carbide ceramic powder prepared in example 1 of the invention.

Detailed Description

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

In one embodiment of the present invention, a layered high-entropy diboron carbide ceramic powder is provided, wherein the layered high-entropy diboron carbide has a chemical formula of REB₂C₂Wherein RE is at least three different elements of Y, Ce, Gd, Dy and Er, and the molar ratio of each element is 1.

In an embodiment of the present invention, a method for preparing the layered high-entropy diboron carbide ceramic powder is provided as follows:

ball-milling and mixing at least three metal oxides, a boron source and a carbon source, compacting the uniformly mixed powder to obtain a densified blank, sintering the blank at a high temperature to obtain a layered high-entropy diboron carbide block material, and finally crushing and grinding to obtain the layered high-entropy diboron carbide powder.

In a specific embodiment, the preparation method comprises the following steps:

(1) weighing at least three metal oxides, a boron source and a carbon source in proportion;

(2) adding a solvent and a ball milling medium, ball milling and mixing raw materials, and performing vacuum drying and sieving to obtain uniformly mixed powder;

(3) hydraulically compacting the uniformly mixed powder, and performing cold isostatic pressing to obtain a densified blank;

(4) carrying out normal-pressure high-temperature sintering treatment on the blank in vacuum or protective atmosphere to obtain a layered high-entropy diboron carbide block material;

(5) and crushing and grinding the block material after high-temperature sintering to finally prepare the layered high-entropy diboron carbide ceramic powder.

Preferably, the metal oxide is selected from yttrium oxide (Y)₂O₃) Cerium oxide (CeO)₂) Gadolinium oxide (Gd)₂O₃) Dysprosium oxide (Dy)₂O₃) Erbium oxide (Er)₂O₃) At least three of them.

Preferably, the boron source is boron carbide (B)₄C) Or Boron Nitride (BN).

Preferably, the carbon source is graphite powder or carbon black.

Preferably, in the step (1), the metal oxide powder is weighed in such an equimolar ratio of the metal elements.

Preferably, in step (1), according to reaction equation A_xO_y+2xBN+(2x+y)C＝xAB₂C₂+xN₂+ yCO the amounts of BN and carbon source required for each metal oxide powder to undergo the thermal reduction reaction of carbon/boron were calculated and then summed to give the total amount of BN and carbon source used.

Preferably, in step (1), according to reaction equation A_xO_y+x/2B₄C+(3/2x+y)C＝xAB₂C₂+ yCO calculation of the B required for each metal oxide powder to undergo the carbon/boron thermal reduction reaction₄C and the amount of the carbon source, and then adding to obtain B₄C and the total amount of carbon source.

Preferably, in the step (2), the ball milling rotation speed is 200-400 rpm, the ball milling time is 10-24 hours, and the ball milling medium is ethanol, propanol, methanol, acetone or water.

Preferably, in the step (2), the vacuum drying temperature is 60-120 ℃, and the drying time is 10-24 h.

Preferably, in the step (3), the hydraulic compaction pressure is 8-15 MPa, and the pressure maintaining time is 5-10 min.

Preferably, in the step (3), the cold isostatic pressing pressure maintaining pressure is 200-300 MPa, and the pressure maintaining time is 10-20 min.

Preferably, in step (4), the selected protective atmosphere is argon or helium.

Preferably, in the step (4), the sintering process is as follows: heating to 1900-2300 deg.C at a rate of 5-20 deg.C/min, holding for 2-5 hr, and cooling to room temperature to obtain the final product. The sintering process can effectively avoid the problems of incomplete reaction between raw materials and incapability of forming a single-phase product caused by low sintering temperature, short heat preservation time and high temperature rise rate.

The invention will be further explained and illustrated with reference to the following examples.

Example 1

(1) Will Y₂O₃、CeO₂、Gd₂O₃、Dy₂O₃、Er₂O₃BN and carbon black are mixed according to the mol ratio of 1:2:1:1:1:20: 36;

(2) mixing the proportioned powder in absolute ethyl alcohol, placing the mixture in a planetary ball mill for ball milling (the rotating speed of the ball mill is 300r/min, the ball milling time is 24 hours), drying the ball-milled powder in vacuum at 80 ℃, and sieving the powder with a 200-mesh sieve to obtain uniformly mixed powder;

(3) placing the uniformly mixed powder into a stainless steel mold, performing hydraulic pressure molding (the pressure maintaining pressure is 15MPa, the pressure maintaining time is 5min), and performing cold isostatic pressing for further molding (the pressure maintaining pressure is 220MPa, the pressure maintaining time is 15min) to obtain a blank;

(4) placing the blank in a graphite crucible, then placing the graphite crucible in a multifunctional sintering furnace, heating to 2000 ℃ at a speed of 10 ℃/min under the argon atmosphere, and preserving heat for 2h to cool the blank to room temperature along with the furnace;

(5) crushing and grinding the block material after high-temperature sintering to finally obtain the layered high entropy (Y)_0.2Ce_0.2Gd_0.2Dy_0.2Er_0.2)B₂C₂Ceramic powder.

FIG. 1 shows the scanning electron microscope morphology of the layered high-entropy diboron carbide ceramic powder prepared in example 1, and it can be seen from FIG. 1 that the powder has an obvious lamellar structure; FIG. 2 is an EDS spectrum of the layered high-entropy diboron carbide ceramic powder prepared in example 1, and from the element surface distribution diagram of 7 elements, the various elements composing the powder are uniformly distributed on a micrometer scale, and no obvious aggregation and segregation are found.

Example 2

(1) Will Y₂O₃、CeO₂、Gd₂O₃、Dy₂O₃、Er₂O₃、B₄C and carbon black are mixed according to the molar ratio of 1:2:1:1:1:5: 31;

(2) mixing the proportioned powder in absolute ethyl alcohol, placing the mixture in a planetary ball mill for ball milling (the rotating speed of the ball mill is 350r/min, the ball milling time is 24 hours), and drying the ball-milled powder in vacuum at 80 ℃ and then sieving the powder with a 200-mesh sieve to obtain uniformly mixed powder;

(3) placing the uniformly mixed powder into a stainless steel mold, performing hydraulic pressure molding (the pressure maintaining pressure is 12MPa, the pressure maintaining time is 10min), and performing cold isostatic pressing for further molding (the pressure maintaining pressure is 220MPa, the pressure maintaining time is 10min) to obtain a blank;

(4) placing the blank in a graphite crucible, placing the graphite crucible in a multifunctional sintering furnace, heating to 1950 ℃ at a speed of 10 ℃/min under the atmosphere of argon, and preserving heat for 3 hours to cool the blank to room temperature along with the furnace;

(5) crushing and grinding the block material after high-temperature sintering to finally obtain the layered high entropy (Y)_0.2Ce_0.2Gd_0.2Dy_0.2Er_0.2)B₂C₂Ceramic powder.

Example 3

(1) Will Y₂O₃、CeO₂、Gd₂O₃、Dy₂O₃、Er₂O₃BN and graphite powder are mixed according to the mol ratio of 1:2:1:1:1:20: 36;

(2) mixing the proportioned powder in propanol, placing the mixed powder in a planetary ball mill for ball milling (the rotating speed of the ball mill is 300r/min, the ball milling time is 20 hours), and drying the ball-milled powder in vacuum at 60 ℃ and then sieving the powder by a 200-mesh sieve to obtain uniformly mixed powder;

(3) placing the uniformly mixed powder into a stainless steel mold, performing hydraulic pressure molding (the pressure maintaining pressure is 10MPa, the pressure maintaining time is 5min), and performing cold isostatic pressing for further molding (the pressure maintaining pressure is 220MPa, the pressure maintaining time is 10min) to obtain a blank;

(4) placing the blank in a graphite crucible, then placing the graphite crucible in a multifunctional sintering furnace, heating to 2100 ℃ at a speed of 10 ℃/min under the argon atmosphere, and preserving heat for 2h to cool the blank to room temperature along with the furnace;

(5) crushing and grinding the block material after high-temperature sintering to finally obtain the layered high entropy (Y)_0.2Ce_0.2Gd_0.2Dy_0.2Er_0.2)B₂C₂Ceramic powder.

Example 4

(1) Will Y₂O₃、Gd₂O₃、Dy₂O₃、Er₂O₃BN and carbon black are mixed according to the mol ratio of 1:1:1:1:16: 28;

(2) mixing the proportioned powder in absolute ethyl alcohol, placing the mixture in a planetary ball mill for ball milling (the rotating speed of the ball mill is 400r/min, the ball milling time is 24 hours), drying the ball-milled powder in vacuum at 100 ℃, and sieving the powder with a 200-mesh sieve to obtain uniformly mixed powder;

(3) placing the uniformly mixed powder into a stainless steel mold, performing hydraulic pressure molding (the pressure maintaining pressure is 12MPa, the pressure maintaining time is 5min), and performing cold isostatic pressing for further molding (the pressure maintaining pressure is 200MPa, the pressure maintaining time is 10min) to obtain a blank;

(4) placing the blank in a graphite crucible, then placing the graphite crucible in a multifunctional sintering furnace, heating to 2000 ℃ at a speed of 10 ℃/min under the argon atmosphere, and preserving heat for 2h to cool the blank to room temperature along with the furnace;

(5) crushing and grinding the block material after high-temperature sintering to finally obtain the layered high entropy (Y)_0.25Gd_0.25Dy_0.25Er_0.25)B₂C₂Ceramic powder.

Example 5

(1) Will Y₂O₃、Gd₂O₃、Dy₂O₃、B₄C and carbon black are mixed according to the mol ratio of 1:1:1:3: 18;

(2) mixing the proportioned powder in propanol, placing the mixed powder in a planetary ball mill for ball milling (the rotating speed of the ball mill is 300r/min, the ball milling time is 24 hours), and drying the ball-milled powder in vacuum at 80 ℃ and then sieving the powder by a 200-mesh sieve to obtain uniformly mixed powder;

(3) placing the uniformly mixed powder into a stainless steel mold, performing hydraulic pressure molding (the pressure maintaining pressure is 12MPa, the pressure maintaining time is 10min), and performing cold isostatic pressing for further molding (the pressure maintaining pressure is 220MPa, the pressure maintaining time is 15min) to obtain a blank;

(4) placing the blank in a graphite crucible, placing the graphite crucible in a multifunctional sintering furnace, heating to 2000 ℃ at a speed of 10 ℃/min under the argon atmosphere, and preserving heat for 3h to cool the blank to room temperature along with the furnace;

(5) crushing and grinding the block material after high-temperature sintering to finally obtain the layered high entropy (Y)_1/3Gd_1/3Dy_1/3)B₂C₂Ceramic powder.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.